Metallic paste pigment



Patented July 4, 1944 3.: M rALLIofrAsTa PIGMENT Leo Lumbar, (lla'yton, Mo. 7

i No Drawing.

sult of the process of grinding or stamping by whichithey areproduced, the particles are in the pplicationl september 18; v1. m; 1 SerialNo.35'1,285-- '12 Claims. o1;.'2s0-31')] I v Antique statuary (oxidized rich gold :pow-

form of thin vflat fiakeswith one dimension considerably'smaller than the others, and these par-' ticles bear a minute filing of grease, such as stearic" acid or palmitic acid, that was mixed with the material" as: a polishing agent during the process of grinding; So-long as the powders; thus produced remain in the condition in which they leave the grinderof-a-stamp mill, they are known as straight run bronze powders. Inall, possibly aldozen basic colors are available in these straight-run powders. The range of colors can be greatly enhanced by heat-treating orox-idizing the powders, i. e., either the true abronze powders or the copper powders. The powders progressively become darker as they are exposed to higher temperatures, or to-a'specific temperature for a longer'periodof time, or to a combination) of both conditions. A' few additional shades can he made by treating certain powders with acetic acid. The effectv of heating straight run 'powders is 'to.= cause the .thinsfiat flakes thereof to curl and to some extent to adhere oragglomerate together. So long as the flakes are thin and flat, they are well suited for" inseam. varnish and lacquer to produce a smooth. coat. with' a large covering capacity; but when the flakes are curled, they'tend to iorm an uneven coat of greatly reduced covering. capacity: 1

Accordingly; it is the object of the present invention to devise a bronze'powder pastewhich answer all the requirements which formerly could only be satisfiedby'the use of a straight run bronze powder in conjunction with a pigmerited lacquer and can be made available in many shades which formerlycould be obtained only with, coarse oxidized bronzes, or by the'use.

of anilinedyed powders. Due to rigid laboratory control in its manufacture the color which my bronze paste yields is always consistent and is not subject to-variations such as are likelywhen othermethodsare used to arrive at-a given color.

following formula is typical of a dark bronze powder in current use:

v Percent Graphite 5.00 Patent red lin-ing' (aniline dyed gold 1 ""po-wder1 10100 'der) v Copperstripping new (straight-run cop- ,per) I Nigger bronze (oxidized pale gold powder),-'- L+.... L;;;.;; Itflis noted that the foregoing bronze powder contains 5 per cent graphite. The presence of this material necessitates eatremeca're in appli} cation as there is a tendency forsu'ch material to float The 10 per cent pf paltent redflin'ing will be a factor in c'au'sing the finish; resulting from this powqer; to be coarsearid' roughjj Moreoi erj the patent color will fadel'up'on exposure to strong light ior any length "of time. Since the d'ye usedin coloring thef'patent coloris soluble in many of the "solvents' used clear' glloss lacquers, it will bleed into"tl'ie top coat which is applied over the coat of bronzing lacquer} This isa desirable feature, but it is difficult "to control sincedifferent sprayoperators' apply the material differently; Thisten'dstoward a lack of color uniformity in production;

I Q "dized pale gold'powders'; which have the disadvantages previously ni entioned, "constitute 'p5 0 per cent oi the powder and will ause theiinish to be. coarse and porous. 'The. zll 'p'ercent of oxi dized rich gold powder has the' same qualities. The remaining 15" per cent or the powder consists of a straight-run copper powders Sincetlfls powder is of a fine texture'it' will tend tomake the finish smooth-and dense, butsince it isrin less proportion than the other powders, its advantages are nullified. j g a a f, A bronze ,powder paste',emhodying the present invention and which duplicates theabove mentioned powder in shade consists of;

s ,Percent Straight-run copper fine 1 31.77 Straight-run green gold 23.56 Carbon blacki 5.09 Lithol red o v1.14 Coumarone-indene resin 21 .86 I-Ii-flash naphtha -s- .a 15.79 Rezyl 869 (long oil alkyd resin). j .79

This paste will hate a greater-coverage thana powder of corresponding colon-This paste will cover 400 square feet per gallon when mixed with abronzing lacquer, forexample, a lacquer comprising 12 percent 6 sec. bronzing nitro-cellulo'se in lacquer thinner, with 4 fluid ounces of 'plasticizer and a; fluid canoes or a medium long drying type alkyd resin to a gallon. "The correspending powder 'when'mix'd with'the same'vehicle at the same ratio, i. e., one pound of powder per gallon will cover 225 square feet per gallon.

The film resulting from the paste is much with alkyclresin of low acid number and a non acid volatile thinner that is free from sulphur, with or without pigment. It also consists in the compositions and process of making same herein after described and claimed.

According to the present invention, {1 -l1 straight run bronze powder made as heretofore by grinding and polishing the metal "a1umi i'uini= copper or zinc or alloys thereof into small 'parti-- cles, such say, as will pass a No. 100 or finer mesh screen. This straight run powder carries a small quantitybfhon-"acid grease, preferably 'stearic acid that was mixed with the metal particle's'at the rate of from four to eightounces per hundred pounds of metallic powder in the process of grinding for the purpose-of polishing the same. 1

This polished metal powder is used without any treatment by heat or otherwise that would cause any oxidation or change. of; color. or that would afiect the thin, flat shape oi the particles. This metal powder is mixed with'alkyd resin and low boiling point naphtha, together with a suitable pigment. The following is a typical example, namely, unoicidized copper 'metal: powder about 55 percent, alkyd resin of low acid num-l ber, say lower than 8, about 17 per cent Hi-fiash naphtha free fromsulphur. and acidity about18 per cent, lamp black 9.75 per centand organic lithol-red .32 per cent. This composition is in the form of a softpaste suitable for packaging and easy to dispense in desired quantities. The naphtha is used as avolatile thinner and its quantity is subject to considerable variation. The alkyd resin is the vehicle or carrier for the metallic particles and other pigment, with which it is quite compatible and/which it preserves against oxidation and sulphidizing. 'A special advantage of alkyd resin is that it is exceptionallywell adapted for grinding and for mixing. with the other. ingredients of .my composition and pre-. serves the color and luster of. the metal particles unimpaired. The term acid number as applied to resin is thenumber of milligrams of potassium hydroxide that are required to neutralize one gram of the particular oil or resin. under question; for example, ifone gram or a resin requires 3 milligramsof potassium hydroxide to neutralize it, then the resin is said to have an acid number of 3.

The quantities of metallic particles, lamp black and other pigments are subject to considerable variations, as the color eifects vary withthe selec.- tion of pigments and'the proportionsin which they are mixed. Itis a great advantage of the present invention that such selections and mixtures can be made by skilled artisans at the face tory and with th assurance that all lots made in accordancewith a'given formula will match even though they may not be used for considerable periods'of time.

In the example specified, about ten per cent of the composition consists of lamp black which 1 15 heat treated to produce substantially the same :jcolorfeftect. -"I have found also that varnishes practice of my invention: pure alkyd resins, as Beckosol No. 1323 and Beckosol No. 1307, phenol modified alkyd resins, as Beckosol No. 1320, oil and phenol modified resins, as Beckosol No. 1, coumarone-indene resins, as cumar, phenol modified coumarone-indene resins, as Nevillac and pure phenolic resins, as Beckacite No. 2000.

The paste hereinbefore described is a rather concentrated preparatiqn and preferably contains"v all desiredpigment so as to be ready for addition to any of the usual varnishes or lacquers.

- -I have found that varnish and lacquer embodying my composition produces a smoother coat-'an'd has greater covering capacity than varnish-or lacquer that embodies bronze powders and-l'acquer embodying my composition require a thinner surface or finish coat of clear lacquer or varnish than is required for other varnishes. What I'claim is: 1 -'l. A"br'onze"paste consisting of straight run bronz powd'er, resin of acidnumber lower than 8 and a volatile-thinner free of sulphur and acidity.

2. A bronze paste consisting of straight run bronze powder, resin'of acidnumber lower than 8 and a volatile thinner .free ofsulphur and acidity. j 3. A bronze paste consis'tingof straight run bronze powder, at least two resins of acid number lower than 8 and volatilethinner freeof sulphur and'acidity.'- i

4. A bronze paste consisting of polished bronze powder in the form of thin fiat particles, resin of acid number lower than 8, a volatile thinner free of sulphur and. 'acidity, and pigment.

'5; A bronze paste consisting of straight run bronze powder, resin of acid number lower than 8 and a volatile thinner free of sulphur and acidity, together with pigment,

6. A bronze paste comprising unoxidized bronze powder in'the" form of thin fiat particles, resin of acid number lower than '8, a volatilethinner free of sulphur and acidity, lamp blackand other pigment. l

' '7. A bronze past'e consisting mainly of polished metallic copper powder in the form of :thin fiat particles free from oxide andsulphide discoloration, resin of acid number lower than 8, 'and naphtha free of sulphur and acidity.

8. A bronze paste consisting mainly of polished metallic copper powder in the form of thin flat particles free from oxide and sulphide discoloration, coumarone-indene resin and an alkyd resin of acid number lower than 8, and naphtha free of sulphur and acidity.

-9. A bronze paste-consisting mainly of straight run metallic copper powder in the form of thin flat particles free from oxide and sulphide discoloration, alkyd resin of acid number lower than 8 and naphtha free'of sulphur and acidity, in substantially the-proportions of three parts of straight run powder to one part of alkyd resin and one partof naphtha.

10. A bronze paste consistingmainly of polished metallig copper powder in the form of thin flat particles free from oxide and sulphide discoloration, alkyd resin of acid number lower than 8 and naphtha free of sulphur and acidity, in substantially the proportions of three parts of powder to one part of alkyd resin and one part of naphtha.

11. A .bronze pastecomprising unoxidize'd bronzepowder in the form oi thin flat particles,

alkyd resin of acid number lower than 8, and naphtha free of sulphur and acidity, and lamp black, in substantially the proportion of 55 parts of bronze powder to 17 parts of alkyd resin, 18

5 parts of naphtha and 10 parts of lamp black.

LEO J. MITCHELL. 

